Women are the fastest growing segment of the HIV/AIDS population, and heterosexual vaginal intercourse is their greatest risk factor. This growth, the lack of clear efficacy of more traditional prevention strategies, and on-going questions about the safety and efficacy of Nonoxynol-9 in the prevention of HIV transmission, demands increased attention to the development of safe, effective vaginal microbicides. As these products are developed and investigated, it is also essential to establish an understanding of how acceptability and use of the products are decided by consumers. The common, one-factor approach of equating acceptability and use fails to capture the complex, contextual nature of microbicide acceptability and use. The present study applies a theoretical framework for understanding acceptability and, ultimately, its use among women at-risk. Guided by the social ecology model, we will consider both product and person-in-context variables. The objective of this work is to elucidate how personal, social, relational, and political variables relate to one another and to a woman's decision to use a microbicidal product. Further, this study will address a limitation in the current state of microbicide acceptability research. That is, the present research will both contribute to a social ecological model of microbicide acceptability and develop a psychometrically sound, quantitative microbicide acceptability instrument. This tool will enable future research to quantify relationships and pathways between person-in-contact factors, product characteristics, intention to use, and actual use of microbicides. The instrument will enable us to compare factor structures across risk groups and will also provide the field with a high quality acceptability measure that will facilitate comparison and consolidation of data across studies. By contributing both to a theoretical and applied understanding of acceptability, and furnishing a sound means of quantifying product acceptability, this work will ultimately increase efficiency of acceptability assessment in upcoming Phase II/III clinical trials of vaginal microbicides, and allow for more successful education and marketing of approved microbicidal products.